The code snippet cited by Cairyn is from the TextureTag manual, maybe a good read to get some more context.

What helped me is the parameter TEXTURETAG_RESTRICTION

You can drag any parameter from Attribute Manager to the Command Line (usually found under the Console) to find out about the ID. In this case, drag the "Selection" label from the Texture tag to the command line.
Another option is to look directly into the resource files in <installation dir>/resource/modules. In this case you'll find c4dplugin/description/ttexture.res.